DE1619993A1 - Process for growing a rod-shaped single crystal from semiconductor material by crucible-free zone melting - Google Patents

Description

■ 'SIEMÜIIS AKTΓΐίΝΰ33SLLGGHAW - Briangen ,; the 2.74RZ. 1967.

Werner-von-oiemens-Str. 50

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Method of growing a rod-shaped Single crystal made of semiconductor material through crucible-free zone melting

The invention relates to a method of growing a rod-shaped Single crystal made of semiconductor material, in particular made of Silicon, by zone melting one of this material without a crucible existing and approximately vertically held rod with a diameter of more than 15 mm, on which a thinner one around its longitudinal axis In rotation, the seed crystal with a diameter of less than 10 mm is melted.

Such «zone melting process with a seed crystal with a Thickness which is substantially less than the thickness of the semiconductor data can for the production of cross-linking-free, single-crystalline

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Semiconductor rods are used. Particularly good successes, i.e. one high yield of dislocation-free, single-crystalline semiconductor rods, can only be achieved if the crucible has free zone melting of semiconductor material with multiple diiches in the melting zone before the last passage through the melting zone, a bottle neck-shaped one Thin section of the semiconductor rod in the immediate vicinity of the melting point of the seed crystal is provided (see German Auslegeschrift 1 079 593).

It has been shown that these are very advantageous in terms of calibration Process for growing monocrystalline semiconductor rods, in particular dislocation-free monocrystalline semiconductor rods, then Difficulties arise when the diameter ratio semiconductor rod / seed crystal becomes large, for example greater than 3 »Special Difficulties are to be expected when at the upper end of a comparatively thick supply rod of, for example, 30 mm or more one for growing a single crystal semiconductor rod a thin seed crystal of, for example 5, should be melted.

The present invention overcomes these difficulties. she is characterized in that in a zone melting process of the type mentioned at the outset, before the seed crystal is melted, it is facing end of the rod by melting, mechanical and / or chemical erosion is so narrowed that its diameter at the Änsahmelzpunkt is at most three times as large as the diameter of the seed crystal.

With a rod diameter of 25 mm or more, part of the tapered rod end is particularly advantageously designed to be cylindrical with a length that is at least almost the same as its diameter. This

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The cylindrical part of the tapered rod end is melted first and because of its limited volume it forms a fairly ' small melting lake from which the single crystal ". Haibieiterstab" after fusing with the tapered end of the supply rod can be drawn. It is irrelevant here whether the tapered End is attached to the top or bottom of the supply rod.

Further details and advantages of the invention are explained in more detail using exemplary embodiments with reference to the drawing. '

Fig. 1 shows a semicircular rod, the lower end of which is according to the invention is shaped.

2a to 2c show different method steps for / growing a Dislocation-free, single-crystalline semiconductor rod from a supply rod, the upper end of which is shaped according to the invention ...

In Fig. 1, a semiconductor rod is denoted by 1, the upper end of which is held in a holder, not shown in the drawing and the lower end of which has a taper 2, which subsequently merges into a cylindrical part 3, with a diameter that ι is much smaller than the burner diameter of the semiconductor rod'1. The cylindrical part 5 of the tapered rod end 2 has a Length at least as great as its thickness. This ensures that when the monocrystalline seed crystal is melted 4 with an inductive heating device5 only the cylindrical one iTei'l 3 of the taper 2 is melted, during the subsequent conical transition 2 sticks «This makes it easier to grow a The single crystalline semiconductor rod is essential. The seed crystal 4 is

; in a holder 6 »preferably orientable, held. the

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inductive heating device 5 can consist of a single or multiple wind There are heating coils, which include the cylindrical part 3 of the semiconductor rod 1 concentrically or, as shown, eccentrically can. The eccentric arrangement of the heating coil 5 facilitates the melting of the cylindrical part 3 of the semiconductor rod 1. After fusing with the seed crystal 4, the heating coil 5 is brought into the concentric position relative to the semiconductor rod 1. In the illustrated Embodiment, the semiconductor rod 1 has a Diameter of 30 mm or more, while the seed crystal has a diameter of about 4 mm. The cylindrical part 3 of the tapered Rod end 2 can now have a diameter between 6 and 9 with a length between 6 and 9 mm. The conical transition 2 has an angle of at most 45 ° to the rod axis. In this way, during manufacture, the tapering 2 is effected by mechanical and / or chemical means Removal of the. Material wear compared to an elongated one Cone kept low. The cylindrical part 3 of the tapered rod end 2 can advantageously by fusing a crystalline Rod part with the conical transition 2 of the semiconductor rod 1 are produced.

In FIGS. 2a to 2c, the same parts are provided with the same reference numerals as in Pig. 1.

In Fig. 2a the seed crystal 4 is against the liquid molten tip of the cylindrical part 3 of the taper 2 and fused with it. The taper 2 is at the upper free end of the Semiconductor rod 1 attached. The inductive heating coil 5 is stationary and attached concentrically to the semiconductor rod 1. After fusing, the semiconductor rod 1 and the seed crystal 4 become

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moved at a speed of about 2.5 mm / min relative to the heating coil 5. The speed of the seed crystal 4 then becomes steadily increased until the one shown in Figures 2b and 2c; bottle neck-shaped thin point 7 has arisen. The thickness of this Thin point 7 can be about 2 to 2.5 mni and its length about 20 mm or - amount to more. The maximum speed of the seed crystal 4 can be more than 20 mm / min. Once the bottle neck-like Thin point 7 has the intended dimensions, the The speed of the seed crystal 4 is slowed down to about 4 to 5 mm / min, so that the thin parts 7 become the conical transition 8 thickened. When the auskri.stallisierende rod part reaches its target diameter has reached, both rod parts are moved at a uniform speed relative to the heating coil. It is an advantage if that Volume of the cylindrical part 3 of the. Tapered rod end .2 is dimensioned so that it becomes a bottle neck-like thin point of can be drawn about 2 mm thick and at least about 20 mm long »

With the method shown in Figures 2a to 2c dislocation-free, monocrystalline semiconductor rods up to one Thickness of more than 30mm can be produced.

Eb it can be seen that the above-described procedure is the same can be used with good success if the upper end of the Semiconductor rod 1 is supported and the taper 2 is attached to the lower end of the rod 1.

The from 'the above description and / or from the associated drawing features, operations and Instructions are, as far as not already known, in detail as well as

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Their combinations with one another, disclosed here for the first time, are to be regarded as valuable inventive improvements.

5 claims
2 figures

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Claims (1)

- - ■ ■. PM 67/1129 ■ '■, · ■■. "■ Claims 1. Method for growing a rod-shaped single crystal from FIG Semiconductor material, in particular made of silicon, through crucible-free Zone melting of an existing one made of this material and approximately vertically held rod with a diameter of more than 15 JMQr to which a thinner, about its longitudinal axis in Rotation offset seed crystal with a diameter of less than 10 mm is melted, characterized in that before the seed crystal (4) melts, the one facing him The end of the rod (1) is tapered by SÖhmelzen, mechanical and / or former removal such that its diameter at the The melting point is at most three times as large as the diameter of the seed crystal (4). 2. The method according to claim 1, characterized in that at one Rod diameter of 25 mm or more a part (5) of the tapered Rod end (2) cylindrical with at least one of its diameter. » almost the same length is formed. 5. The method according to claim 2, characterized in that ium attaching a seed crystal (4) with a diameter of approximately 4 mm to a rod (t) mii; a diameter ψ * η 50 mm or ι more the cylindrical part (3) of the tapered rod end (2) with: a Durehmeoser · between 6 and 9 mm, with a length between j. '^;"■""". ■ '■ ·'. "■""■"":""* - ■ '" -: - ".-" ■■ ' "* - 6 · and 9 is now formed -.- and the subsequent conical transition (2) has an angle of no more than 45 ° to the rod axis. PLA 67/1129 t 4. The method according to claim 1, characterized in that the cylindrical part (3) of the tapered rod end (2) by fusing a crystalline rod part with the semiconductor rod (1-manufactured will. 5. Method according to one of Claims 1 to 4, characterized in that that the volume of the cylindrical part (3) of the tapered rod end (2) se is dimensioned that therefrom a bottle neck-shaped Thin point (7) about 2 mm thick and about 20 mm long can be drawn. BATH ORIGINAL